Internal combustion engines are used in a wide variety of applications. As a result of the internal combustion process, such engines necessarily generate exhaust emissions having a variety of carbon-based and other substances. Increasingly it desired that internal combustion engines be capable of operating in a manner such that at least one or more components of these exhaust emissions from the engines are reduced or eliminated.
Further, legislation has recently been (or is in the process of being) enacted in various jurisdictions such as California placing restrictions on the exhaust emissions of small off-road engines such as those employed in various small off-road vehicles and other small vehicles that are used to perform various functions in relation to the environment, for example, lawn mowers and snow blowers.
Catalytic converter technology is the most commonly implemented technology for processing exhaust emissions from internal combustion engines. In particular, catalytic converters and/or catalytic mufflers are now employed in most automobiles. Nevertheless, conventional catalytic converter technology has several disadvantages that make it not highly desirable, for use in many applications such as the above-mentioned small off-road engines.
In particular, catalytic converters tend to be fairly complicated and expensive due to their use of precious metal catalysts. Further, catalytic converters tend to lack durability and tend to deteriorate over time, both in terms of their substrates and metal catalysts as well as in terms of the wash coat applied to the precious metal catalysts, the latter being negatively impacted in particular by high temperature gases and lubrication-oil chemicals. Short periods of exposure to extreme thermal excursions during operation under “off-normal” conditions are also problematic in this regard.
Therefore, it would be advantageous if an improved system (or systems) could be developed for processing exhaust emissions produced by internal combustion engines including, for example, small off-road engines. Further, it would be advantageous if, in at least some embodiments, such improved system did not require the use of a catalytic converter, and was relatively inexpensive and more durable in comparison with conventional catalytic converters.